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Web filter installer

WebInstallersBundle / WebFilterInstaller

Register new filter in main or admin contexts.

Recognition

Detects classes annotated with @javax.servlet.annotation.WebFilter annotation and register them in dropwizard environment.

@WebFilter("/some/*")
public class MyFilter implements Filter { ... }

Only the following annotation properties are supported: filterName, urlPatterns (or value), servletNames, dispatcherTypes, initParams, asyncSupported.

Warning

Url patterns and servlet names can't be used at the same time.

Filter name is not required. If name not provided, then it will be generated as: . (dot) at the beginning to indicate generated name, followed by lower-cased class name. If class ends with "filter" then it will be cut off. For example, for class "MyCoolFilter" generated name will be ".mycool".

Tip

Use guicey @Order annotation to order servlets registration.

@Order(10)
@WebFilter("/some/*")
public class MyFilter implements Filter { ... }

There is a difference between using filter installer and registering filters with guice servlet module: guice servlet module handles registered servlets and filters internally in GuiceFilter (which is installed by guicey in both app and admin contexts). As a side effect, there are some compatibility issues between guice servlets and native filters (rare and usually not blocking, but still).

Installer use guice only for filter instance creation and register this instance directly in dropwizard environment (using annotation metadata).

Async

Example of async filter definition:

@WebFilter(urlPatterns = "/asyncfilter", asyncSupported = true)
public class AsyncFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        final AsyncContext context = request.startAsync();
        context.start(() -> {
            context.getResponse().writer.write("done!");
            context.complete();
        });
    }

    @Override
    public void destroy() {
    }
}

Note that guice servlet module does not allow using async filters, so installer is the only option to install async filters.

Admin context

By default, installer target application context. If you want to install into admin context then use guicey @AdminContext annotation.

For example:

@AdminContext
@WebFilter("/some/*")
public class MyFilter implements Filter { ... }

Will install filter in admin context only.

If you want to install in both contexts use andMain attribute:

@AdminContext(andMain = true)
@WebFilter("/some/*")
public class MyFilter implements Filter { ... }